if you mean that you want to remove the passive radiator in your T500,s then bock off the open hole and run the T500 as a sealed cabinet and augment the low bass with and active (powered) sub then sure I would say that was a good idea. But if you are suggesting that you remove the passive radiator from the T500 then install a second woofer into where the passive was and run it in either parallel or series with the existing woofer then no that would be a non productive thing to do since you would need to re design your speaker to make such an idea work, it is just not a useful way for you to spend your time or money. In case you are not sure about what a passive radiator does it has the exact same function as a reflex vent in that it is a resonating mass which couples in antiphase to the woofer to provide damping/control to the woofer when it plays low enough to reach the system resonance. It is like an acoustical break which is frequency controlled it couples with the woofer adding a mass to the woofer which then alters (lowers) the resonant frequency of the woofer. This process happens over a very narrow band of frequency of only 5 or 6 Hz. and without it to damp or control the woofer it would reach the system resonant point and begin to resonate at full excursion and if left undamped would proceed to tear itself to pieces. I hope this helps you to understand things a little better. If you want more bass add a sub or two. removing the passive and blocking it off with a plywood blank would turn your speakers into a sealed box design. A reflex box whether it is designed with a vent or a passive radiator has a roll off of 24 db per octave below the tuning frequency while a sealed box rolls off at only 12db per octave below system or box resonance, so you will actually get lower frequency extension and more useful output with the box sealed. This would involve re damping the cabinet. There is a caveat and that is that almost all reflex designs have an intentional hump in the bass response somewhere prior to system or box resonance this is intended to make the woofer provide a little more umph. With a sealed box you will loose the additional bass hump in the response but since it rolls off so much slower you will attain lower bass frequency extension. There is no "free lunch" you decide what you want to achieve. Good of you to ask your question because you are not the only person to have wondered about this. The more questions you ask the more you will know and hopefully the easier your audio journey will be. Remember the fun is in the journey and not the destination.